In general, the amount of supported component (in particular noble metals of Group VIII) is the smallest possible, provided that, the other conditions remaining the same, the same results or better results are obtained than those obtained when greater quantities of catalytic component are used. In other words, the aim is that of raising the ratio "carrier/catalytic compound" to a maximum. When the catalyst is used, for instance, in the form of a powder dispersed in a liquid reaction medium, the waste of catalytic component in some instances may be considerable, because of the more or less partial solubility of the component in the reaction liquid, as well as because of the loss during the separation of the catalyst from the end product, for instance by filtering or by centrifuging.